Notopterygium Incisum Extract Promotes Apoptosis by Preventing the Degradation of BIM in Colorectal Cancer

Colorectal cancer (CRC), a prevalent malignancy worldwide, has prompted extensive research into anticancer drugs. Traditional Chinese medicinal materials offer promising avenues for cancer management due to their diverse pharmacological activities. This study investigated the effects of Notopterygium incisum, a traditional Chinese medicine named Qianghuo (QH), on CRC cells and the underlying mechanism.

The sulforhodamine B assay and colony formation assay were employed to assess the effect of QH extract on the proliferation of CRC cell lines HCT116 and Caco-2. Propidium iodide (PI) staining was utilized to detect cell cycle progression, and PE Annexin V staining to detect apoptosis. Western blotting was conducted to examine the levels of apoptotic proteins, including B-cell lymphoma 2-interacting mediator of cell death (BIM), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (BAX) and cleaved caspase-3, as well as BIM stability after treatment with the protein synthesis inhibitor cycloheximide. The expression of BAX was suppressed using lentivirus-mediated shRNA to validate the involvement of the BIM/BAX axis in QH-induced apoptosis. The in vivo effects of QH extract on tumor growth were observed using a xenograft model. Lastly, APC^Min+ mice were used to study the effects of QH extract on primary intestinal tumors.

QH extract exhibited significant in vitro anti-CRC activities evidenced by the inhibition of cell proliferation, perturbation of cell cycle progression, and induction of apoptosis. Mechanistically, QH extract significantly increased the stability of BIM proteins, which undergo rapid degradation under unstressed conditions. Knockdown of BAX, the downstream effector of BIM, significantly rescued QH-induced apoptosis. Furthermore, the in vitro effect of QH extract was recapitulated in vivo. QH extract significantly inhibited the tumor growth of HCT116 xenografts in nude mice and decreased the number of intestinal polyps in the APC^Min+ mice.

QH extract promotes the apoptosis of CRC cells by preventing the degradation of BIM.